Over the weekend, Comet 46P/Wirtanen made history. The green ball of gas wrapped around a nugget of dirty ice flew past Earth only 11.5 million km away--so close that it cracked the top 10 list of comet flybys during the Space Age. During the hours of closest approach, 46P/Wirtanen appeared in the constellation Taurus alongside the Pleiades star cluster:
Michael Jäger took the picture on Dec. 16th from Turmkogel, Austria. "To create the image, I combined 6-minute exposures through red, green and blue filters," says Jäger.
The colors in Jäger's image are remarkable--a striking contrast of green vs. blue. Wirtanen's green comes from diatomic carbon (C2)--a gaseous substance common in comet atmospheres that glows green in the near-vacuum of space. The Pleiades, on the other hand, appear blue because the stars themselves are that color. Hot and massive, the Seven Sisters shine their blue light into surrounding clouds of gas and dust, which reflect the azure hue.
46P/Wirtanen is receding from Earth now, but it will still be nearby for days to come. The main challenge for observers is not distance, but rather moonlight. The glare of the waxing Moon will dilute the comet's brightness, making it a challenge to see with the unaided eye. Digital cameras and widefield telescopes will have no trouble, however, capturing the comet's exit. It is currently glowing like a big misty star of 4th magnitude near the horns of the Bull:
The colors in Jäger's image are remarkable--a striking contrast of green vs. blue. Wirtanen's green comes from diatomic carbon (C2)--a gaseous substance common in comet atmospheres that glows green in the near-vacuum of space. The Pleiades, on the other hand, appear blue because the stars themselves are that color. Hot and massive, the Seven Sisters shine their blue light into surrounding clouds of gas and dust, which reflect the azure hue.
46P/Wirtanen is receding from Earth now, but it will still be nearby for days to come. The main challenge for observers is not distance, but rather moonlight. The glare of the waxing Moon will dilute the comet's brightness, making it a challenge to see with the unaided eye. Digital cameras and widefield telescopes will have no trouble, however, capturing the comet's exit. It is currently glowing like a big misty star of 4th magnitude near the horns of the Bull:
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